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United States Patent | 5,528,940 |
Yamamoto ,   et al. | June 25, 1996 |
A differential pressure transmitter having a differential pressure sensor, a temperature sensor and a static pressure sensor all provided on the semiconductor substrate of a single semiconductor chip. A reference resistor is provided in a part of the chip. Resistances of the differential pressure sensor and the reference resistor are compared periodically in order to determine the condition including service life of the differential pressure sensor.
Inventors: | Yamamoto; Yoshimi (Naka-machi, JP); Tobita; Tomoyuki (Katsuta, JP) |
Assignee: | Hitachi, Ltd. (Tokyo, JP) |
Appl. No.: | 190847 |
Filed: | February 3, 1994 |
Feb 10, 1993[JP] | 5-022358 |
Current U.S. Class: | 73/708; 73/720; 73/726; 338/42; 374/198 |
Intern'l Class: | G01L 019/04; H01C 010/10 |
Field of Search: | 73/708,719,720,721,725,726,727,754 338/36,42 374/198 |
4468968 | Sep., 1984 | Kee | 73/708. |
4598381 | Jul., 1986 | Cucci | 73/708. |
4872349 | Oct., 1989 | Espiritu-Santo | 73/708. |